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61.
Xiaoqing Liu Chuncheng Li Guohu Guan Xuepei Yuan Yaonan Xiao Dong Zhang 《Journal of Polymer Science.Polymer Physics》2005,43(19):2694-2704
The melting behavior, crystallization behavior, and morphology of PBSR, which is Poly(butylene succinate) modified with rosin maleopimaric acid anhydride (RMA), were investigated with differential scanning calorimetry (DSC) and polarized optical microscope (POM). The multiple endotherms were ascribed to the recrystallization during DSC measurement and the equilibrium melting temperature determined by the Peak L, which was associated with the fusion of the crystals grown by normal primary crystallization, was 125.9 °C. After the kinetic parameters for isothermal crystallization of PBSR were determined by Avrami equation, to make a detailed regime transition analysis, the well‐established Lauritzen–Hoffman equation was employed. The results indicated that there were two regimes, regime II and regime III, in the range of higher and lower crystallization temperature, respectively. The regime transition temperature is about 81 °C. At last, the spherulitic morphologies of PBSR after being crystallized isothermally at different temperature were observed with the help of POM. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2694–2704, 2005 相似文献
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Crosslinking is an effective way to improve polymer properties. This paper focuses on ultraviolet‐induced crosslinking of poly(butylene succinate) (PBS) in the presence of a photoinitiator and a crosslinking agent at ambient temperature. The effects of the concentration of photoinitiator, the crosslinking agent content, and the irradiation time on the crosslink behavior were investigated. To obtain an appropriate gel fraction in different irradiation times, 3.0 wt% of photoinitiator and 10.0 wt% of crosslinking agent were proved to be the optimum choice. Furthermore, properties such as thermal properties, dynamic mechanical property, and enzymatic degradation of PBS before and after crosslinking were examined. Differential scanning calorimetry (DSC) analysis revealed that glass transition temperature (Tg) increased with increase in gel fraction, while melting temperature (Tm) and the degree of crystallinity decreased. This may be caused by the reduced molecular chain mobility and inhibited molecular motion for crystallization in crosslinked samples. The crosslinked polymer also showed improved thermal stability and dynamic mechanical property. In addition, the introduction of crosslinking retarded the enzymatic degradation rate of PBS, but it was still biodegradable. The improved properties of crosslinked PBS will extend the application of PBS. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Efficient synthesis of ionic triblock copolyesters and facile access to charge‐reversal hybrid micelles 下载免费PDF全文
Shaohua Wu Liuchun Zheng Wen Zhou Chuncheng Li Yaonan Xiao Wenxiang Zhu 《Journal of polymer science. Part A, Polymer chemistry》2016,54(9):1259-1267
Novel carboxyl‐ and amino‐functionalized copolyesters, based on poly(ε‐caprolactone)‐block‐poly(butylene fumarate)‐block‐poly(ε‐caprolactone), were efficiently synthesized via Michael‐type thiol‐ene click chemistry. The resulting amphiphilic copolyesters with controllable molecular weights and abundant positively or negatively charged groups could spontaneously form pH‐sensitive micelles in aqueous solutions, as confirmed by transmission electron microscopy, dynamic light scattering, fluorescence probing technique, and zeta potential analyses. Importantly, charge‐reversal hybrid micelles can be obtained by co‐assembly of carboxyl‐ and amino‐functionalized copolyesters. The surface charges of hybrid micelles reversed rapidly from negative to positive at isoelectric point via protonation of surface carboxyl and amino groups. Interestingly, the hybrid micelles showed apparent pH‐triggered Nile red‐release behavior in acidic condition resembling tumor intracellular environment, which is fairly desirable for drug delivery. Our work indicates that co‐assembly is a facile but efficient way to prepare charge‐reversal micelles, which have great potential to be used as intelligent drug delivery systems for cancer therapy. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1259–1267 相似文献
66.
Qi Wang Dr. Chuncheng Chen Prof. Wanhong Ma Prof. Huaiyong Zhu Prof. Jincai Zhao Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(19):4765-4769
Synergistic interactions between N and F can be used to tune the band structures of N‐doped TiO2 (see scheme). Reduction potential of conduction band electron is positively shifted to weaken unwanted O2 reduction, but enhances the target reduction reaction in air. The tuning also enhances the oxidation ability of the valence band to oxidize water to O2, which makes photocatalytic reduction proceed without any organic sacrificial reagents.
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Carbon-encapsulated copper nanoparticles were synthesized by a modified arc plasma method using methane as carbon source.
The particles were characterized in detail by transmission electron microscope, high-resolution transmission electron microscopy,
selected-area electron diffraction, X-ray diffraction, thermogravimetric and differential scanning calorimetry. The encapsulated
copper nanoparticles were about 30 nm in diameter with 3–5 nm graphitic carbon shells. The outside graphitic carbon layers
effectively prevented unwanted oxidation of the copper inside. The effect of the ratio of He/CH4 on the morphologies and the formation of the carbon shell were investigated. 相似文献
69.
Force field development for organic molecules: Modifying dihedral and 1–n pair interaction parameters 下载免费PDF全文
Siyan Chen Shasha Yi Wenmei Gao Chuncheng Zuo Zhonghan Hu 《Journal of computational chemistry》2015,36(6):376-384
We comprehensively illustrate a general process of fitting all‐atom molecular mechanics force field (FF) parameters based on quantum mechanical calculations and experimental thermodynamic data. For common organic molecules with free dihedral rotations, this FF format is comprised of the usual bond stretching, angle bending, proper and improper dihedral rotation, and 1–4 scaling pair interactions. An extra format of 1–n scaling pair interaction is introduced when a specific intramolecular rotation is strongly hindered. We detail how the preferred order of fitting all intramolecular FF parameters can be determined by systematically generating characteristic configurations. The intermolecular Van der Waals parameters are initially taken from the literature data but adjusted to obtain a better agreement between the molecular dynamics (MD) simulation results and the experimental observations if necessary. By randomly choosing the molecular configurations from MD simulation and comparing their energies computed from FF parameters and quantum mechanics, the FF parameters can be verified self‐consistently. Using an example of a platform chemical 3‐hydroxypropionic acid, we detail the comparison between the new fitting parameters and the existing FF parameters. In particular, the introduced systematic approach has been applied to obtain the dihedral angle potential and 1–n scaling pair interaction parameters for 48 organic molecules with different functionality. We suggest that this procedure might be used to obtain better dihedral and 1–n interaction potentials when they are not available in the current widely used FF. © 2014 Wiley Periodicals, Inc. 相似文献
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Frontispiece: Inverse Kinetic Solvent Isotope Effect in TiO2 Photocatalytic Dehalogenation of Non‐adsorbable Aromatic Halides: A Proton‐Induced Pathway 下载免费PDF全文